Conversion‐Derived Hierarchical Li‐In/Li ₂ O Interphase for Dendrite‐Free Lithium Metal Batteries With Suppressed Anode‐to‐Cathode Crosstalk

The practical use of lithium metal anodes is hindered by dendrite growth, unstable solid electrolyte interphase (SEI) formation, and anode‐to‐cathode crosstalk, particularly when paired with high‐nickel cathodes. Herein, a scalable strategy is reported to construct an In 2 O 3 nanolayer on a copper foil via magnetron sputtering. During initial lithiation, this layer irreversibly converts into a Li‐In/Li 2 O composite interphase. The lithiophilic Li‐In alloy inner layer lowers the nucleation barrier, while the in situ‐formed Li 2 O matrix acts as a high‐modulus framework that constrains the alloy phase, suppresses parasitic electrolyte reduction, and directs the formation of a robust, inorganic‐dominated SEI. The engineered anode achieves 98.5% coulombic efficiency over 500 cycles in half‐cells, and sustains stable symmetric‐cell operation for over 11 000 h. In full cells with LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM90) cathodes, the anodic stabilization suppresses anode‐to‐cathode crosstalk, leading to a thin, uniform cathode electrolyte interphase (CEI) that preserves the morphological and structural integrity of the NCM90 cathode. Under stringent conditions (negative‐to‐positive ratio = 1.5, 3 µL mAh −1 , 60°C, 4.4 V), the cell retains 82.4% capacity after 100 cycles. A 6.5 Ah anode‐free pouch cell delivers 508.6 Wh kg −1 with 81.7% capacity retention after 40 cycles, underscoring the scalability and practical viability of this interfacial engineering approach.